1. Field of the Invention
The present invention relates to the field of mass spectrometry for determining the amino acid sequence of proteins or peptides.
2. Disclosure of the Related Art
Some of the known processes for derivatization of proteins or peptides to sulfonic acid derivatives are carried out by directly reacting a sulfonic acid or a sulfonyl group-containing compound with the N-terminus of proteins or peptides. A drawback of this approach is that the reaction species have strongly acidic groups that affect the reaction efficiency at the N-terminus of proteins or peptides.
In one technique, reagents such as 2-sulfobenzoic acid cyclic anhydride and chlorosulfonylacetyl chloride are used to introduce sulfonic acid groups at the N-terminus of peptides (Proc. Natl. Acad. Sci. USA Vol. 96, pp. 7131-7136, June 1999).
It is not possible, however, to selectively collect the N-terminal fragments or selectively derivatize the N-terminal fragments to sulfonic acid derivatives by using the technique, since, according to this technique, the reagents are applied to tryptic peptides.